Korzh V, Sleptsova I, Liao J, He J, Gong Z
Institute of Molecular Agrobiology, National University of Singapore, Singapore.
Dev Dyn. 1998 Sep;213(1):92-104. doi: 10.1002/(SICI)1097-0177(199809)213:1<92::AID-AJA9>3.0.CO;2-T.
Two zebrafish bHLH genes, neurogenin-related gene I (ngn1) and neuroD (nrd), have been isolated. ngn1 expression is initiated at the end of gastrulation in the neural plate and defines broad domains of cells that probably possess an ability to develop as neurons. This finding suggests that ngn1 may play a role during determination of cell fate in neuroblasts. ngn1 and pax-b are expressed in a mutually exclusive manner. nrd expression follows that of ngn1 in restricted populations of cells selected from ngn1-positive clusters of cells. The earliest nrd-positive cells in the brain and the trunk are a subset of the primary neurons. ngn1 is not expressed in the eye. Here, nrd transcription is activated at 25 hours postfertilization in the ventral retina. Expression of islet-1 occurs in nrd-positive cells after expression of nrd, and the expression of the two genes partially overlaps in time. These observations suggest that during eye development nrd expression may follow expression of some other neurodetermination gene(s). This supports the idea that expression of nrd is a necessary step leading toward overt neuronal differentiation.
已经分离出两个斑马鱼bHLH基因，即神经生成素相关基因I（ngn1）和神经分化因子（nrd）。ngn1的表达在原肠胚形成末期于神经板开始，并界定了可能具有发育为神经元能力的广泛细胞区域。这一发现表明，ngn1可能在成神经细胞的细胞命运决定过程中发挥作用。ngn1和pax-b以相互排斥的方式表达。nrd的表达在从ngn1阳性细胞簇中挑选出的特定细胞群体中跟随ngn1的表达。脑和躯干中最早的nrd阳性细胞是初级神经元的一个子集。ngn1在眼睛中不表达。在此，受精后25小时，nrd转录在腹侧视网膜中被激活。胰岛-1的表达在nrd表达之后出现在nrd阳性细胞中，并且这两个基因的表达在时间上部分重叠。这些观察结果表明，在眼睛发育过程中，nrd的表达可能跟随某些其他神经决定基因的表达。这支持了nrd的表达是通向明显神经元分化的必要步骤这一观点。
